Present embodiments relate to a gas turbine engine. More particularly, but not by way of limitation, present embodiments relate to a rotor off-take aperture in the stator vane.
In the gas turbine engine, air is pressurized in a compressor and mixed with fuel in a combustor for generating hot combustion gases which flow downstream through turbine stages. These turbine stages extract energy from the combustion gases. A high pressure turbine includes a first stage nozzle and a rotor assembly having a disk and a plurality of turbine blades. The high pressure turbine first receives the hot combustion gases from the combustor and includes a first stage stator nozzle that directs the combustion gases downstream through a row of high pressure turbine rotor blades extending radially outwardly from a first rotor disk. In a two stage turbine, a second stage stator nozzle is positioned downstream of the first stage blades followed in turn by a row of second stage turbine blades extending radially outwardly from a second rotor disk. The stator nozzles direct the hot combustion gas in a manner to maximize extraction at the adjacent downstream turbine blades.
The first and second rotor disks are joined to the compressor by a corresponding high pressure rotor shaft for powering the compressor during operation. These are typically referred to as the high pressure turbine. The gas turbine engine may include a number of stages of static air foils, commonly referred to as vanes, interspaced in the engine axial direction between rotating air foils commonly referred to as blades. A multi-stage low pressure turbine follows the two stage high pressure turbine and is typically joined by a second low pressure shaft to a fan disposed upstream from the compressor in a typical turbofan aircraft engine configuration for powering an aircraft in flight.
The stator is formed by a plurality of nozzle segments which are abutted at circumferential ends to form a complete ring about the axis of the gas turbine engine. Each nozzle segment may comprise a single vane, commonly referred to as a singlet. Alternatively, a nozzle segment may have two vanes per segment, which are generally referred to as doublets. In a third embodiment, additional numbers of vanes may be disposed on a single segment. In these embodiments, the vanes extend between an inner band and an outer band.
As the combustion gases flow downstream through the turbine stages, energy is extracted therefrom and the pressure of the combustion gas is reduced. The extracted energy rotates the turbine and the compressor. In this manner, fuel energy is converted to mechanical energy of the rotating shaft to power the compressor and supply compressed air needed to continue the process.
In the current state of the art, rotor bleed off-take systems utilize a gap between a vane exit and a rotor inlet for bleed extraction. In these current systems, the off-take requires air turning from the stator inner flow surface at an angle of about 90 degrees, and sometimes even more, to move between the fixed stator flow surface and the adjacent rotor inlet. However, one problem with the current state of the art is that as the air turns from the stator vane exit, the air encounters the turning structure of the adjacent rotor which causes swirl of the air and pressure drops in the sealed cavity area. Additionally, since the air turns 90 degrees, very little available kinetic head is utilized to drive the flow of the bleed air to the off-take cavity.
Because of these configurations, it would be desirable to reduce pressure drops when the bleed air moves from above the stator flow surface to within the off-take cavity. It may also be desirable to increase pressure recovery while also reducing swirl which occurs due to rotation in the area where air encounters rotor rotation. It would be further desirable to use sufficiently higher dynamic pressure to drive this flow and increase pressure recovery at the flow off-take source.
It would be desirable to improve these characteristics through the use of high kinetic head to drive bleed air through the off-take cavity while reducing vortex and providing pressure recovery to the bleed air.
The information included in this Background section of the specification, including any references cited herein and any description or discussion thereof, is included for technical reference purposes only and is not to be regarded subject matter by which the scope of the instant embodiments are to be bound.